Genetics: cortex gene darkens moths and colours butterflies

Nature

June 2, 2016

A gene responsible for the colours and colour patterns on the wings of butterflies and moths has been independently identified in two separate studies published in this week’s Nature. This gene, and a mutation associated with it, controlled the darkening of the peppered moth that took place during the Industrial Revolution, and the gene is also responsible for the natural colour pattern variation in certain butterfly species, the studies find.

It is well known that the rise of industrial cities led to the darkening of the peppered moth (Biston betularia) - an adaptive response to pollution and bird predation. However, in earlier studies the specific mutation that led to the common, pale (typica) form being replaced by a previously unknown black form (carbonaria) had only broadly been localized and constrained as acting on a DNA region containing 13 genes.

Ilik Saccheri and colleagues identify the genetic background and precise sequence mutation behind the carbonaria form of the peppered moth. They find that the mutation resulted from insertion of a large portion of DNA sequence into a gene called cortex. They also conducted a phylogenetic analysis that pinpoints the origin of this mutation to around 1819, when the Industrial Revolution was beginning. In a separate study, Nicola Nadeau and colleagues used population genomics and gene expression analyses to reveal that the expression of cortex varies with colour patterning in butterflies of the genus Heliconius. Collectively, these findings suggest that a novel, basic mechanism may underlie colour patterning in the order Lepidoptera, which includes moths and butterflies.